Re: oops during scsi scanning disk setup

[Chris Webb <chris@arachsys.com>]

Chris Webb <chris@arachsys.com> writes:

> James Bottomley <James.Bottomley@suse.de> writes:
> 
> > Actually, if that works, I'll have the above backported as well.
> 
> Hi James. That's much better; thanks! I certainly can't provoke any problems
> with it in a VM, although I couldn't really reproduce the problem with the
> original kernel in a test environment either. I'll push it to our clusters
> and see how things go over the next week or so.

We've been running with this for a couple of weeks now, and I haven't seen the
crash repeat itself. That said, I applied this on top to see if I could detect
the race:

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1936,6 +1936,8 @@
 
 	sd_printk(KERN_NOTICE, sdkp, "Attached SCSI %sdisk\n",
 	          sdp->removable ? "removable " : "");
+	if (atomic_read(&sdkp->dev.kobj.kref.refcount) < 2)
+		sd_printk(KERN_WARNING, sdkp, "Attempted to release device before sd_probe_async complete\n");
 	put_device(&sdkp->dev);
 }

and it hasn't triggered at all, so I wonder whether we've just not hit the bug again.

Best wishes,

Chris.